Portuguese succession crisis of 1580 in the context of "John IV of Portugal"

The War of the Portuguese Succession, a result of the extinction of the Portuguese royal line after the Battle of Alcácer Quibir and the ensuing Portuguese succession crisis of 1580, was fought from 1580 to 1583 between the two main claimants to the Portuguese throne: António, Prior of Crato, proclaimed in several towns as King of Portugal, and his first cousin Philip II of Spain, who eventually succeeded in claiming the crown, reigning as Philip I of Portugal.

The Iberian Union or the Hispanic Monarchy, describes the period from 1580 to 1640 in which the Monarchy of Spain under the Habsburg dynasty, then the personal union of the crowns of Castile and Aragon, brought in personal union also the Kingdom of Portugal. It incorporated the entire Iberian Peninsula except Andorra, as well as Portuguese and Spanish overseas possessions, under the Spanish Habsburg monarchs Philip II, Philip III, and Philip IV. The union began after the Portuguese succession crisis of 1580 and the ensuing War of the Portuguese Succession, and lasted until the Portuguese Restoration War, during which the House of Braganza was established as Portugal's new ruling dynasty with the acclamation of John IV as the new king of Portugal.

As a personal union, the Kingdom of Portugal, the Crown of Castile and the states of the Crown of Aragon remained independent states, sharing only a single monarch. The kings from the Spanish branch of the House of Habsburg were the only element that connected the multiple kingdoms and territories, ruled by the six separate government councils of Castile, Aragon, Portugal, Italy, Flanders-Burgundy, and the Indies. For periods, Portugal maintained a viceroy, appointed by the king, although the turnover was often rapid; in the 60 years of the Union, the country had 13 viceroys and four regency councils (see List of viceroys of Portugal). Similar viceroys were appointed in Aragon, Catalonia, Valencia and other kingdoms of the Union. The governments, institutions, and legal traditions of each kingdom remained independent of one another. Alien laws (Leyes de extranjería) determined that a national of one kingdom was a foreigner in all other kingdoms.

The Restoration War (Portuguese: Guerra da Restauração) between Portugal and Spain began with the Portuguese revolution of 1640 and ended with the Treaty of Lisbon in 1668, bringing a formal end to the Iberian Union.The period from 1640 to 1668 was marked by periodic skirmishes between Portugal and Spain, as well as short episodes of more serious warfare, much of it occasioned by Spanish and Portuguese entanglements with non-Iberian powers. Spain was involved in the Thirty Years' War until 1648 and the Franco-Spanish War until 1659, while Portugal was involved in the Dutch–Portuguese War until 1663.

In the 17th century and afterwards, this period of sporadic conflict was simply known, in Portugal and elsewhere, as the Acclamation War. The war established the House of Braganza as Portugal's new ruling dynasty, replacing the House of Habsburg, which had been united with the Portuguese crown since the 1580 succession crisis.

António, Prior of Crato (European Portuguese pronunciation: [ɐ̃ˈtɔni.u, ɐ̃ˈtɔnju]; 1531 – 26 August 1595), sometimes called "The Determined", "The Fighter", "The Independentist" or "The Resistant", was a grandson of King Manuel I of Portugal who claimed the Portuguese throne during the 1580 dynastic crisis. According to some historians, he was King of Portugal for 33 days in 1580. Philip II of Spain prevailed in the succession struggle, but António claimed the throne until 1583. He was a disciple of Bartholomew of Braga.

The Anglo-Portuguese Alliance (Portuguese: Aliança Luso-Inglesa, "Luso-English Alliance") is the oldest alliance that is still in force by political bilateral agreement. It was established by the Treaty of Windsor in 1386, between the Kingdom of England (since succeeded by the United Kingdom) and the Kingdom of Portugal (now the Portuguese Republic), though the countries were previously allied via the Anglo-Portuguese Treaty of 1373.

Since the signing of the Treaty of Windsor, the Kingdom of Portugal and the Kingdom of England, and later the modern Portuguese Republic and United Kingdom, have never waged war against each other, nor have they participated in wars on opposite sides as independent states (with one brief exception as described below). While Portugal was subsumed under the Iberian Union, rebellious Portuguese factions and government in exile sought refuge and help in England. England spearheaded the Anglo-Spanish War (1585–1604) on the side of the deposed Portuguese royal house.

Infanta Catherine of Portugal, Duchess of Braganza by marriage (Portuguese: Catarina; Portuguese pronunciation: [kɐtɐˈɾinɐ], 18 January 1540 – 15 November 1614) was a Portuguese infanta (princess) claimant to the throne during the Portuguese succession crisis of 1580.